Altered Phospholipid Composition Research Articles

Propionate Decreases Microglial Activation but Impairs Phagocytic Capacity in Response to Aggregated Fibrillar Amyloid Beta Protein.

Microglia, the innate immune cell of the brain, are a principal player in Alzheimer's disease (AD) pathogenesis. Their surveillance of the brain leads to interaction with the protein aggregates that drive AD pathogenesis, most notably Amyloid Beta (Aβ). Microglia attempt to clear and degrade Aβ using phagocytic machinery, spurring damaging neuroinflammation in the process. Thus, modulation of the microglial response to Aβ is crucial in mitigating AD pathophysiology. SCFAs, microbial byproducts of dietary fiber fermentation, are blood-brain barrier permeable molecules that have recently been shown to modulate microglial function. It is unclear whether propionate, one representative SCFA, has beneficial or detrimental effects on microglia in AD. Thus, we investigated its impact on microglial Aβ response in vitro. Using a multiomics approach, we characterized the transcriptomic, metabolomic, and lipidomic responses of immortalized murine microglia following 1 h of Aβ stimulation, as well as characterizing Aβ phagocytosis and secretion of reactive nitrogen species. Propionate blunted the early inflammatory response driven by Aβ, downregulating the expression of many Aβ-stimulated immune genes, including those regulating inflammation, the immune complement system, and chemotaxis. Further, it reduced the expression of Apoe and inflammation-promoting Aβ-binding scavenger receptors such as Cd36 and Msr1 in favor of inflammation-dampening Lpl, although this led to impaired phagocytosis. Finally, propionate shifted microglial metabolism, altering phospholipid composition and diverting arginine metabolism, resulting in decreased nitric oxide production. Altogether, our data demonstrate a modulatory role of propionate on microglia that may dampen immune activation in response to Aβ, although at the expense of phagocytic capacity.

Lipid metabolism analysis providing insights into nonylphenol multi-toxicity mechanism

Nonylphenol (NP), a widely recognized endocrine disruptor, exhibits lipophobic properties that drive its accumulation in adipose tissue, leading to various physiological disruptions. Using Caenorhabditis elegans, this study investigated the effects of NP exposure on lipid homeostasis and physiological indicators. NP exposure increased lipid storage, hindered reproduction and growth, and altered phospholipid composition. Transcriptional analysis revealed NP's promotion of lipogenesis and inhibition of lipolysis. Metabolites related to lipid metabolism like citrate, amino acids, and neurotransmitters, along with lipids, collectively influenced physiological processes. This work elucidates the complex link between lipid metabolism disturbances and NP-induced physiological disruptions, enhancing our understanding of NP's multifaceted toxicity.

Selective expression of light-harvesting complexes alters phospholipid composition in the intracytoplasmic membrane and core complex of purple phototrophic bacteria

Phospholipid–protein interactions play important roles in regulating the function and morphology of photosynthetic membranes in purple phototrophic bacteria. Here, we characterize the phospholipid composition of intracytoplasmic membrane (ICM) from Rhodobacter (Rba.) sphaeroides that has been genetically altered to selectively express light-harvesting (LH) complexes. In the mutant strain (DP2) that lacks a peripheral light-harvesting (LH2) complex, the phospholipid composition was significantly different from that of the wild-type strain; strain DP2 showed a marked decrease in phosphatidylglycerol (PG) and large increases in cardiolipin (CL) and phosphatidylcholine (PC) indicating preferential interactions between the complexes and specific phospholipids. Substitution of the core light-harvesting (LH1) complex of Rba. sphaeroides strain DP2 with that from the purple sulfur bacterium Thermochromatium tepidum further altered the phospholipid composition, with substantial increases in PG and PE and decreases in CL and PC, indicating that the phospholipids incorporated into the ICM depend on the nature of the LH1 complex expressed. Purified LH1–reaction center core complexes (LH1–RC) from the selectively expressing strains also contained different phospholipid compositions than did core complexes from their corresponding wild-type strains, suggesting different patterns of phospholipid association between the selectively expressed LH1–RC complexes and those purified from native strains. Effects of carotenoids on the phospholipid composition were also investigated using carotenoid-suppressed cells and carotenoid-deficient species. The findings are discussed in relation to ICM morphology and specific LH complex–phospholipid interactions.

Itraconazole Modulates Phospholipid Levels in Tumor-associated Macrophages.

Itraconazole, an antifungal drug, repolarizes pro-tumorigenic M2 tumor-associated macrophages to anti-tumorigenic M1-like phenotypes, thereby inhibiting the proliferation of cancer cells; however, the underlying mechanism remains unclear. Therefore, we investigated the effect of itraconazole on membrane-associated lipids in tumor-associated macrophages (TAM). M1 and M2 macrophages were derived from the human monocyte leukemia cell line (THP-1) and cultured with or without 10 μM itraconazole. Cells were homogenized and subjected to liquid chromatography/mass spectrometry (LC/MS) analysis to estimate the glycerophospholipid levels in the cells. Lipidomic analysis results, displayed on a volcano plot, revealed that itraconazole-induced altered phospholipid composition, with more pronounced changes in M2 macrophages than in M1. Notably, itraconazole significantly increased intracellular phosphatidylinositol and lysophosphatidylcholine levels in M2 macrophages. Itraconazole modulates the lipid metabolism of TAMs, which could have implications for the development of novel cancer therapies.

Pseudomonas aeruginosa responds to altered membrane phospholipid composition by adjusting the production of two-component systems, proteases and iron uptake proteins

Membrane protein and phospholipid (PL) composition changes in response to environmental cues and during infections. To achieve these, bacteria use adaptation mechanisms involving covalent modification and remodelling of the acyl chain length of PLs. However, little is known about bacterial pathways regulated by PLs. Here, we investigated proteomic changes in the biofilm of P. aeruginosa phospholipase mutant (∆plaF) with altered membrane PL composition. The results revealed profound alterations in the abundance of many biofilm-related two-component systems (TCSs), including accumulation of PprAB, a key regulator of the transition to biofilm. Furthermore, a unique phosphorylation pattern of transcriptional regulators, transporters and metabolic enzymes, as well as differential production of several proteases, in ∆plaF, indicate that PlaF-mediated virulence adaptation involves complex transcriptional and posttranscriptional response. Moreover, proteomics and biochemical assays revealed the depletion of pyoverdine-mediated iron uptake pathway proteins in ∆plaF, while proteins from alternative iron-uptake systems were accumulated. These suggest that PlaF may function as a switch between different iron-acquisition pathways. The observation that PL-acyl chain modifying and PL synthesis enzymes were overproduced in ∆plaF reveals the interconnection of degradation, synthesis and modification of PLs for proper membrane homeostasis. Although the precise mechanism by which PlaF simultaneously affects multiple pathways remains to be elucidated, we suggest that alteration of PL composition in ∆plaF plays a role for the global adaptive response in P. aeruginosa mediated by TCSs and proteases. Our study revealed the global regulation of virulence and biofilm by PlaF and suggests that targeting this enzyme may have therapeutic potential.

Ablation of pigment epithelium-derived factor receptor (PEDF-R/Pnpla2) causes photoreceptor degeneration

Photoreceptor cells express the patatin-like phospholipase domain-containing 2 (PNPLA2) gene that codes for pigment epithelium-derived factor receptor (PEDF-R) (also known as ATGL). PEDF-R exhibits phospholipase activity that mediates the neurotrophic action of its ligand PEDF. Because phospholipids are the most abundant lipid class in the retina, we investigated the role of PEDF-R in photoreceptors by generating CRISPR Pnpla2 knock-out mouse lines in a retinal degeneration-free background. Pnpla2−/− mice had undetectable retinal Pnpla2 gene expression and PEDF-R protein levels as assayed by RT-PCR and immunofluorescence, respectively. The photoreceptors of mice deficient in PEDF-R had deformities as examined by histology and transmission electron microscopy. Pnpla2 knockdown diminished the PLA2 enzymatic activity of PEDF-R in the retina. Lipidomic analyses revealed the accumulation of lysophosphatidyl choline-DHA and lysophosphatidyl ethanolamine-DHA in PEDF-R-deficient retinas, suggesting a possible causal link to photoreceptor dysfunction. Loss of PEDF-R decreased levels of rhodopsin, opsin, PKCα, and synaptophysin relative to controls. Pnpla2−/− photoreceptors had surface-exposed phosphatidylserine, and their nuclei were TUNEL positive and condensed, revealing an apoptotic onset. Paralleling its structural defects, PEDF-R deficiency compromised photoreceptor function in vivo as indicated by the attenuation of photoreceptor a- and b-waves in Pnpla2−/− and Pnpla2+/− mice relative to controls as determined by electroretinography. In conclusion, ablation of PEDF-R in mice caused alteration in phospholipid composition associated with malformation and malperformance of photoreceptors. These findings identify PEDF-R as an important component for photoreceptor structure and function, highlighting its role in phospholipid metabolism for retinal survival and its consequences.

Exploring the potential effect of phospholipase A2 antibody to extend beef shelf-life in a beef liposome model system

The objective of this study was to elucidate the effect of phospholipase A2 (PLA2) and a PLA2 antibody (aPLA2) on phospholipid (PL) hydrolysis in beef and to understand how the altered PL composition may affect lipid oxidation and antioxidant capacity of beef in an in vitro system. Various combinations of PLA2 and aPLA2 were introduced to a beef liposome model system and exposed to a retail display. The PL and free fatty acid (FFA) profiles, antioxidant capacity and lipid oxidation were measured for the liposome system. Key PL classes were reduced and the release of polyunsaturated FFAs was increased with the inclusion of PLA2 in the treatments (P < 0.05). There was no inhibition of PL hydrolysis with the addition of aPLA2. PLA2 showed strong antioxidant capacity in the liposome system (P < 0.01), but lipid oxidation still increased in samples treated with PLA2 throughout the retail display (P < 0.01). Finally, aPLA2 treatments demonstrated potential to decrease lipid oxidation (P < 0.01).

An ER phospholipid hydrolase drives ER-associated mitochondrial constriction for fission and fusion.

Mitochondria are dynamic organelles that undergo cycles of fission and fusion at a unified platform defined by endoplasmic reticulum (ER)-mitochondria membrane contact sites (MCSs). These MCSs or nodes co-localize fission and fusion machinery. We set out to identify how ER-associated mitochondrial nodes can regulate both fission and fusion machinery assembly. We have used a promiscuous biotin ligase linked to the fusion machinery, Mfn1, and proteomics to identify an ER membrane protein, ABHD16A, as a major regulator of node formation. In the absence of ABHD16A, fission and fusion machineries fail to recruit to ER-associated mitochondrial nodes, and fission and fusion rates are significantly reduced. ABHD16A contains an acyltransferase motif and an α/β hydrolase domain, and point mutations in critical residues of these regions fail to rescue the formation of ER-associated mitochondrial hot spots. These data suggest a mechanism whereby ABHD16A functions by altering phospholipid composition at ER-mitochondria MCSs. Our data present the first example of an ER membrane protein that regulates the recruitment of both fission and fusion machineries to mitochondria.

Lipidomic analysis of surfactant and plasma from horses with asthma and age-matched healthy horses.

To perform lipidomic analysis of surfactant and plasma from asthmatic and healthy horses. 30 horses with clinical signs of asthma and 30 age-matched control horses. Detailed history, physical examination, CBC, and bronchoalveolar lavage fluid (BALF) cytologies were obtained. Asthmatic horses were grouped based on their BALF inflammatory profile: severe equine asthma (SEA), mild equine asthma with neutrophilic airway inflammation (MEA-N), or mild equine asthma with eosinophilic airway inflammation (MEA-E). Each asthma group was assigned its own age-matched control group. Lipidomic analysis was completed on surfactant and plasma. Surfactant protein D (SP-D) concentrations were measured in serum and BALF. SEA surfactant was characterized by a phospholipid deficit and altered composition (increased ceramides, decreased phosphatidylglycerol, and increased cyclic phosphatidic acid [cPA]). In comparison, MEA-N surfactant only had a decrease in select phosphatidylglycerol species and increased cPA levels. The plasma lipidomic profile was significantly different in all asthma groups compared to controls. Specifically, all groups had increased plasma phytoceramide. SEA horses had increased plasma cPA and diacylglycerol whereas MEA-N horses only had increased cPA. MEA-E horses had increases in select ceramides and dihydrocermides. Only SEA horses had significantly increased serum SP-D concentrations. The most significant surfactant alterations were present in SEA (altered phospholipid content and composition); only mild changes were observed in MEA-N horses. The plasma lipidomic profile was significantly altered in all groups of asthmatic horses and differed among groups. Data from a larger population of asthmatic horses are needed to assess implications for diagnosis, prognosis, and treatment.

Mesenchymal stem cell-derived exosomes altered neuron cholesterol metabolism via Wnt5a-LRP1 axis and alleviated cognitive impairment in a progressive Parkinson’s disease model

Parkinson’s disease (PD) is associated with abnormal metabolism of brain cholesterol, and the metabolites of neuronal cholesterol may also affect neurodegenerative progression. In this study, we aim to explore the therapeutic effect of BMSC derived exosomes on motor and cognitive deficits in α-synuclein (α-Syn) A53T transgenic mice, a progressive PD animal model. Results revealed that rotating rod performance of α-Syn A53T TG mice decreased by 45.4 %±8.6 % at the age of 12 months compared with wide-type (WT) mice. Striatum injection of BMSC quiescent exosomes (BMSCquiescent-EXO) and BMSC induced exosomes (BMSCinduced-EXO) rescued the rotation behavior (BMSCquiescent-EXO: 92.3 %±12.5 % P = 0.008; BMSCinduced-EXO: 102.3 %±16.7 %, P = 0.006). Although there was no difference in the escape latency within 5 days of Morris water maze learning between groups in the 12-month old mice. The exploration latency was shorter (p < 0.05) in BMSCquiescent-EXO and BMSCinduced-EXO groups, the number of explorations and novel object recognition index were significantly increased (p < 0.05). More importantly, the total cholesterol level was increased (p < 0.05), while the content of 24S-hydroxycholesterol significantly decreased (p < 0.05) after intrastriatal injection BMSCquiescent-EXO and BMSCinduced-EXO in A53T group. Liquid chromatography-mass spectrometry (LC/MS) was performed to profile phospholipid metabolites in lipid raft of hippocampal neurons, demonstrating that BMSCquiescent-EXO injection caused the decreasing relative percentages of phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) compared to those in A53T mice, while the relative percentages of phosphatidylinositol (PI), phosphatidylserine (PS), and phosphatidylcholine (PC) increased. The cholesterol content of lipid rafts was lower in BMSCquiescent-EXO and BMSCinduced-EXO groups than that in A53T group (P < 0.05). In summary, exosomes isolated during BMSC dopaminergic neuron differentiation can significantly improve the motor, learning and memory ability of the progressive PD mice model, and its mechanism may be related to the change of altered phospholipid composition and cholesterol metabolism in hippocampal neurons.

Pseudomonas Aeruginosa Responds to Altered Membrane Phospholipid Composition by Adjusting the Production of Two-Component Systems, Proteases and Iron Uptake Proteins

Pseudomonas Aeruginosa Responds to Altered Membrane Phospholipid Composition by Adjusting the Production of Two-Component Systems, Proteases and Iron Uptake Proteins

Exposure to per- and polyfluoroalkyl substances associates with an altered lipid composition of breast milk.

The composition of human breast milk is highly variable inter- and intra-individually. Environmental factors are suspected to contribute to such compositional variation, however, their impact on breast milk composition is currently poorly understood. We sought to (1) define the impact of maternal exposure to per- and polyfluoroalkyl substances (PFAS) on lipid composition of human breast milk, and (2) to study the combined impact of maternal PFAS exposure and breast milk lipid composition on the growth of the infants.In a mother-infant study (n=44) we measured the levels of PFAS and lipids in maternal serum and conducted lipidomics analysis of breast milk collect 2-4days after the delivery and at 3months of infant age, by using ultra high performance liquid chromatography combined with quadrupole-time-of-flight mass spectrometry. Gastrointestinal biomarkers fecal calprotectin and human beta defensin 2 were measured in the stool samples at the age of 3, 6, 9, and 12months. Maternal diet was studied by a validated food frequency questionnaire. PFAS levels were inversely associated with total lipid levels in the breast milk collected after the delivery. In the high exposure group, the ratio of acylated saturated and polyunsaturated fatty acids in triacylglycerols was increased. Moreover, high exposure to PFAS associated with the altered phospholipid composition, which was indicative of unfavorable increase in the size of milk fat globules. These changes in the milk lipid composition were further associated with slower infant growth and with elevated intestinal inflammatory markers. Our data suggest that the maternal exposure to PFAS impacts the nutritional quality of the breast milk, which, in turn, may have detrimental impact on the health and growth of the children later in life.

Protein arginine methyltransferase 8 modulates mitochondrial bioenergetics and neuroinflammation after hypoxic stress.

Protein arginine methyltransferases (PRMTs) are a family of enzymes involved in gene regulation and protein/histone modifications. PRMT8 is primarily expressed in the central nervous system, specifically within the cellular membrane and synaptic vesicles. Recently, PRMT8 has been described to play key roles in neuronal signaling such as a regulator of dendritic arborization, synaptic function and maturation, and neuronal differentiation and plasticity. Here, we examined the role of PRMT8 in response to hypoxia-induced stress in brain metabolism. Our results from liquid chromatography mass spectrometry, mitochondrial oxygen consumption rate, and protein analyses indicate that PRMT8(-/-) knockout mice presented with altered membrane phospholipid composition, decreased mitochondrial stress capacity, and increased neuroinflammatory markers, such as tumor necrosis factor alpha and ionized calcium binding adaptor molecule 1 (Iba1, a specific marker for microglia/macrophage activation) after hypoxic stress. Furthermore, adenovirus-based overexpression of PRMT8 reversed the changes in membrane phospholipid composition, mitochondrial stress capacity, and neuroinflammatory markers. Together, our findings establish PRMT8 as an important regulatory component of membrane phospholipid composition, short-term memory function, mitochondrial function, and neuroinflammation in response to hypoxic stress.

Abstract PS17-26: Fatty acid synthase inhibition targets ERα in tamoxifen-resistant breast cancer

Abstract INTRODUCTION: Estrogen receptor-positive (ER+) breast cancer accounts for nearly 70% of all cases. Common targeted anti-estrogen therapies such tamoxifen, fulvestrant and aromatase inhibitors have shown success in the clinic, but unfortunately, often lead to resistance. The fatty acid synthase enzyme (FASN) is responsible for endogenously synthesizing long-chain fatty acids, such as palmitate, which can contribute to protein modification, phospholipid biosynthesis for membranes, and lipid raft signaling that favors tumorigenesis. The depletion of intracellular palmitate leads to an alteration of lipid composition within lipid rafts of the plasma membrane as well as lipids within the endoplasmic reticulum membrane. Endoplasmic reticulum stress elicits an inhibition of protein translation through the phosphorylation of eukaryotic initiating factor 2-α (p-eIF2α) and is activated by various stimuli including altered phospholipid composition within the membrane. Our preliminary findings illustrated a degradation of the ERα upon treatment with the FASN inhibitor, TVB-3166, in tamoxifen-resistant breast cancer both in vivo and in vitro. Moreover, previous studies have illustrated FASN inhibition to induce endoplasmic reticulum stress concomitant with a loss of the androgen receptor (AR) in castration-resistant prostate cancer. Additionally, palmitate treatment rescued AR expression that was accompanied by an attenuation in endoplasmic reticulum stress. HYPOTHESIS: We hypothesize FASN inhibition leads to a degradation of ERα in tamoxifen-resistant breast cancer through the induction of endoplasmic reticulum stress. METHODS: Patient tumor explants were incubated for 72h on gelatin sponges in culture medium in the absence or presence of 200nM TVB-3166. Tissue were fixed in 10% formalin and processed into paraffin blocks and stained for ERα and Ki67. To investigate TVB induced endoplasmic reticulum stress, tamoxifen-Resistant (TamR) MCF-7 and MCF-7 cells were treated with TVB-3166 or vehicle control followed by treatment with either palmitate or ER stress inhibitor, 1,2-Bis(2-Aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA). Expression of ERα, p-eIF2α, eIF2α were measured by western blot. RESULTS: TVB-3166 treatment of primary tumor explants decreased their proliferation (Ki67) compared to untreated controls (14% vs 36%, p&amp;lt;0.01). Both IHC and Western blotting demonstrated a reduction in ERα upon treatment with TVB-3166. In addition to the decreased expression of ERα, there was an increase in the phosphorylation of eukaryotic initiation factor 2α (p-eIF2α). The expression of ERα was rescued upon palmitate treatment while resulting in decreased p-eIF2α. Inhibition of endoplasmic stress using BAPTA also rescued ERα expression after TVB-3166 treatment. CONCLUSION: FASN is a potentially viable target in tamoxifen-resistant breast cancer. Citation Format: Bryan Mcclellan, Aleksandra Gruslova, Christopher Jolly, Linda deGraffenried, Andrew Brenner. Fatty acid synthase inhibition targets ERα in tamoxifen-resistant breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-26.

Electrostatic Effects on Model Membrane Compressibility and Vesicle Adhesion

Though vesicles are recognized as effective drug carriers and functionalized with polymers, targeting ligands, imaging agents, and antibodies for drug delivery applications, there is minimal knowledge of the role of lipid bilayer properties in a vesicle's ability to interact with target membranes. Phospholipids within the cellular lipid membrane are chemically diverse, with tail lengths, saturation, and headgroup chemistry varying depending on tissue function and health condition. These function and status dependent compositional observations raise questions on how the underlying membrane properties, such as thickness, fluidity, and compressibility, alter biophysical processes and regulate the transport of vesicles across the membrane. In this work we use compositionally controlled, free-standing large area model biomembranes (LAMB) as an artificial platform to investigate the ramifications of altered phospholipid composition on vesicle-membrane interactions. First, simultaneous area and capacitance measurements of the LAMB allow us to determine the thickness and Young's modulus (compressibility) of a given membrane of varied compositions. In particular, we focus on the effect of headgroup charge, which shows that increasing anionic phospholipid composition increases the membrane stiffness. Next, small (100nm) vesicles composed of DOPC, DOPE, and DOPE-Rh are introduced and subsequently electrostatically adhered to the LAMB. We use Ca2+ ions as a trigger to initiate fusion between the adhered vesicles and LAMB while monitoring fluorescence and capacitance. We observe interesting morphological changes at the membrane interface such as vesicle-vesicle fusion, formation of worm-like vesicle aggregates, and vesicle-membrane fusion. Current work is focused analyzing these events and calculating the activation energy of membrane fusion by simultaneous fluorescence and capacitance measurements. Characterizing the relationship between energy of fusion and vesicle/membrane composition will provide a basis for the rational design of vesicles for targeted membrane interaction.

Intestinal Phospholipid Disequilibrium Initiates an ER Stress Response That Drives Goblet Cell Necroptosis and Spontaneous Colitis in Mice.

Background & AimsPatients with ulcerative colitis have low concentrations of the major membrane lipid phosphatidylcholine (PC) in gastrointestinal mucus, suggesting that defects in colonic PC metabolism might be involved in the development of colitis. To determine the precise role that PC plays in colonic barrier function, we examined mice with intestinal epithelial cell (IEC)-specific deletion of the rate-limiting enzyme in the major pathway for PC synthesis: cytidine triphosphate:phosphocholine cytidylyltransferase-α (CTαIKO mice).MethodsColonic tissue of CTαIKO mice and control mice was analyzed by histology, immunofluorescence, electron microscopy, quantitative polymerase chain reaction, Western blot, and thin-layer chromatography. Histopathologic colitis scores were assigned by a pathologist blinded to the experimental groupings. Intestinal permeability was assessed by fluorescein isothiocyanate–dextran gavage and fecal microbial composition was analyzed by sequencing 16s ribosomal RNA amplicons. Subsets of CTαIKO mice and control mice were treated with dietary PC supplementation, antibiotics, or 4-phenylbutyrate.ResultsInducible loss of CTα in the intestinal epithelium reduced colonic PC concentrations and resulted in rapid and spontaneous colitis with 100% penetrance in adult mice. Colitis development in CTαIKO mice was traced to a severe and unresolving endoplasmic reticulum stress response in IECs with altered membrane phospholipid composition. This endoplasmic reticulum stress response was linked to the necroptotic death of IECs, leading to excessive loss of goblet cells, formation of a thin mucus barrier, increased intestinal permeability, and infiltration of the epithelium by microbes.ConclusionsMaintaining the PC content of IEC membranes protects against colitis development in mice, showing a crucial role for IEC phospholipid equilibrium in colonic homeostasis. SRA accession number: PRJNA562603.

PE homeostasis rebalanced through mitochondria-ER lipid exchange prevents retinal degeneration in Drosophila.

The major glycerophospholipid phosphatidylethanolamine (PE) in the nervous system is essential for neural development and function. There are two major PE synthesis pathways, the CDP-ethanolamine pathway in the endoplasmic reticulum (ER) and the phosphatidylserine decarboxylase (PSD) pathway in mitochondria. However, the role played by mitochondrial PE synthesis in maintaining cellular PE homeostasis is unknown. Here, we show that Drosophila pect (phosphoethanolamine cytidylyltransferase) mutants lacking the CDP-ethanolamine pathway, exhibited alterations in phospholipid composition, defective phototransduction, and retinal degeneration. Induction of the PSD pathway fully restored levels and composition of cellular PE, thus rescued the retinal degeneration and defective visual responses in pect mutants. Disrupting lipid exchange between mitochondria and ER blocked the ability of PSD to rescue pect mutant phenotypes. These findings provide direct evidence that the synthesis of PE in mitochondria contributes to cellular PE homeostasis, and suggest the induction of mitochondrial PE synthesis as a promising therapeutic approach for disorders associated with PE deficiency.

Protein Binding to Lipid Droplets with Altered Ratios of Surface Phospholipids

Alcoholic Fatty Liver Disease (AFLD) is characterized by an increase in lipid droplets in the liver after acute ingestion of alcohol. Previous experiments with a rat model of AFLD show hepatic lipid droplets contain altered levels of the predominant classes of phospholipids. Specifically, hepatic lipid droplets from AFLD rats were found with lower amounts of phosphatidylcholine (PC) relative to phosphatidylethanolamine (PE). Our experiments aim to determine if the altered phospholipid composition of AFLD lipid droplets causes differences in the numbers or types of lipid droplet‐associated proteins. We selected proteins based on their membrane binding motifs and roles in lipid droplet homeostasis. AML12 cells cultured in choline‐deficient media simulate the altered phospholipid composition of AFLD lipid droplets. We isolated lipid droplets from AML12 cells cultured with and without choline and examined proteins of interest by SDS‐PAGE and western blotting. We found equivalent levels of rab18 and lanosterol synthase in lipid droplet fractions from cells grown with and without choline. Alternatively, perilipin 1, perilipin 2, and CIDE‐C are predominantly found in lipid droplet fractions from cells grown without choline (with lower ratios of PC:PE). The proteins that are most influenced by lipid droplet surface composition are all predicted to associate with lipid droplets through amphipathic alpha helices. By evaluating how altered phospholipid monolayer composition affects the binding of lipid droplet proteins, we seek to further elucidate the biochemical pathways that contribute to AFLD.Support or Funding InformationThis research was supported by St. Olaf College and the TRIO McNair Scholars Program.

Liver Disease and Hemostasis (Review) Part 2. Cholestatic Liver Disease and Hemostasis

The presence or development of liver disorders can significantly complicate the course of critical illness and terminal conditions. Systemic hemostatic disorders are common in Intensive Care Units patients with cholestatic liver diseases, so the study of the mechanisms of their development can contribute to the understanding of the development of multiorgan failure in critical illness.The review discusses current data on changes in hemostatic parameters in patients with cholestatic liver diseases, proposes a mechanism for the development of such disorders, which involve interactions of phospholipids with platelet and endotheliocyte membranes. It is suggested that a trend for thrombosis in patients with cholestatic liver disease is due to increased accumulation of bile acids in the systemic circulation. Available data demonstrate that the antiphospholipid syndrome may predispose to the formation of blood clots due to alterations of phospholipid composition of membranes of platelets and vascular endothelial cells by circulating antiphospholipid antibodies. Clarifying the mechanisms contributing to changes of the blood coagulation system parameters in liver disorders will aid to development of optimal correction of hemostatic disorders in patients with chronic liver diseases.

Glioma Stem Cell-Specific Superenhancer Promotes Polyunsaturated Fatty-Acid Synthesis to Support EGFR Signaling.

Glioblastoma ranks among the most aggressive and lethal of all human cancers. Functionally defined glioma stem cells (GSC) contribute to this poor prognosis by driving therapeutic resistance and maintaining cellular heterogeneity. To understand the molecular processes essential for GSC maintenance and tumorigenicity, we interrogated the superenhancer landscapes of primary glioblastoma specimens and in vitro GSCs. GSCs epigenetically upregulated ELOVL2, a key polyunsaturated fatty-acid synthesis enzyme. Targeting ELOVL2 inhibited glioblastoma cell growth and tumor initiation. ELOVL2 depletion altered cellular membrane phospholipid composition, disrupted membrane structural properties, and diminished EGFR signaling through control of fatty-acid elongation. In support of the translational potential of these findings, dual targeting of polyunsaturated fatty-acid synthesis and EGFR signaling had a combinatorial cytotoxic effect on GSCs. SIGNIFICANCE: Glioblastoma remains a devastating disease despite extensive characterization. We profiled epigenomic landscapes of glioblastoma to pinpoint cell state-specific dependencies and therapeutic vulnerabilities. GSCs utilize polyunsaturated fatty-acid synthesis to support membrane architecture, inhibition of which impairs EGFR signaling and GSC proliferation. Combinatorial targeting of these networks represents a promising therapeutic strategy.See related commentary by Affronti and Wellen, p. 1161.This article is highlighted in the In This Issue feature, p. 1143.